Is it possible to add descriptions for the yas-choose-value choices?

Question

I got a simple snippet for the opening a file in PHP:

fopen('${1:./filename.txt}', '${2:$$(yas-choose-value '("r" "w" "a" "x" "r+" "w+" "a+" "x+"))}') or die();

So when I get to the choose the file opening mode, r,w,a,x... I get the dropdown:

r
w
a
.

But I would like to add a description of whats the function of each mode, like:

r   - Open read only
w   - Open for write erases content
.
.

Is it possible to do this with yas-choose-value?

Answer 1

I would suggest using an alist of choices, with the car being the choice+description and the cdr being the actual choice. There are a variety of options that yasnippet offers for user input (see yas-prompt-functions with a default value of yas-dropdown-prompt, yas-completing-prompt, yas-maybe-ido-prompt, and yas-no-prompt), some of which may not support an alist of choices. As indicated in a comment above, the user is not confined to either yas-choose-value or yas-completing-read. The key ingredient is (unless (or yas-moving-away-p yas-modified-p) ...) with the ... needing to be replaced with the custom Lisp that does whatever you want. Here is a custom example that uses ido:

fopen('${1:./filename.txt}', '${2:$$(unless (or yas-moving-away-p yas-modified-p)
  (require 'ido)
  (let* ((choices-alist '(("r - Open read only" . "r")
                          ("w - Open for write erases content" . "w")
                          ("a - The 'a' description." . "a")
                          ("x - The 'x' description." . "x")
                          ("r+ - The 'r+' description." . "r+")
                          ("w+ - The 'w+' description." . "w+")
                          ("a+ - The 'a+' description." . "a+")
                          ("x+ - The 'x+' description." . "x+")))
         (choice (ido-completing-read "Please choose one:  " choices-alist nil 'confirm)))
    (cdr (assoc choice choices-alist))))}') or die();

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The following ticket requests that the Emacs team implement support for ido tab completion using an alist collection, and I have provided a draft proof concept for said implementation: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=46091